Downdraft carburetor



J. H. POHLMAN DOWND'RAF'T. CARBURETOR Dc.V 23, 1,969

3 Sheets-Sheet 1 Filed June 20, 1967 m 7 mL 4 l Z @H w104 .W 3 Z 0 WW 1 N Z/ MH M W W aa Z Ir H j@ ,IH f .f n. W HV l if NH4 HHN: V1 r1H 0 me 5 T \1 no@ au \/,/,l |I| b@ afm@ |11. I ,9 a f l i ,A w -M Il 1 .NW9 8 xllb y v ./w TWD@ m L /Ag w MM@ I Z MM M Vlf w y 1 A 4 HM J A, 4 6 m .4 TTO/Q/VEV Dac. 23, 1969 l J., H. POHLMAN. l 3,485,483

IIOYRJDR'FTV CARBURETOR.

Filed June 2O,V 1967 3 Sheets-'Sheet 2.

14 "A y@ Q INVENTOR. JOHN H. 100M/.MAN

. 16% ff/fm2 wrom/5V Dec. 23, 11969 J.. H, PQHLMAN 3,485,483 DowNDRAFT CARHURMOR Filed June. 20. les? s 'sheets-sheen;

1N VENTOR.

JOHA//UHMA/v BY g 35 Arme/vir United States Patent O 3 Claims ABSTRACT OF THE DISCLOSURE A downdraft carburetor having a fuel inlet provided with a combined fuel filter and vapor separator, with means to return the vapors to the fuel tank, and embodying an integral pressure regulator so only liquid fuel at a predetermined pressure is fed to the carburetor; having either automatic cam, diaphragm or piston means, to pro vide increased fuel flow that increases idling speed, enriches the mixture under cold Weather or other cold-starting conditions, and under throttle control; and having means to vent excessive pressures as caused by backfires and the like.

CROSS-REFERENCE TO RELATED APPLICATION Reference is made to pending application Ser. No. 580,488, over which the present novel features are improvements.

BACKGROUND OF THE INVENTION The present carburetor includes, as an integral part thereof, a combination fuel filter and vapor separator utilizing a means of returning vapor to the fuel tank, thereby feeding only filtered liquid fuel to the engine; an internal pressure regulator pre-set to a fixed and constant relief pressure with the excess being bypassed for return to the tank together with the gas vapors; an automatic mechanism acting to enable fuel enrichment when needed, as when the engine is cold, when the throttle is opened from the idling position of no throttle, and when faster idling speed is desired; and a valve assembly that yields to and vents backfire gases, thereby protecting the elements of the valve.

The invention has for an object to provide a carburetor embodying the above novel and automatic features.

This invention also has for its objects to provide such means that are positive in operation, convenient in use, easily installed in a working position and easily disconnected therefrom, economical of manufacture, relatively simple, and of general superiority and serviceability.

The invention also comprises novel details of construction and novel combinations and arrangements of parts, which will more fully appear in the course of the following description, which is based on the accompanying drawings. However, said drawings merely show, and the following description merely describes, preferred embodir ments of the present invention, which are given by way of illustration or example only.

SUMMARY OF 'TH-E INVENTION The present carburetor, generally, comprises a housing that is adapted to be connected at the top to an air intake and at the bottom to the suction or intake of an internal combustion engine, means 11 to filter liquid fuel, as gasoline, kerosene, etc., from an inlet 12 and to accumulate vapors of said fuel above the level of the filtered fuel, a pre-set pressure regulator 13 for maintaining predetermined pressure on said fuel so the outlet 14 for said fuel remains at a constant pressure, the regulator including a bypass 15 that opens under excess pressure to return excess fuel to the tank serving said engine with fuel, a metering valve assembly 1'6 to receive the flow from the outlet 14, a fuelametering disc 17 disposed in a 3,485,483 Patented Dec. 23, 1969 ice l through passage 1-8 and embodying a metering needle 19 that comprises part of the metering valve assembly 16, a spring 20 to bias the disc 17 to valve-closing or nearly closed position, a position-limiting accelerator arm 21 controlled by a level 22, which is connected to and controlled by the throttle or accelerator pedal of the vehicle on which the carburetor is provided, means 23 for resiliently retaining the valve assembly in normal fiowclosing position, and means 24 to automatically increase metered flow of the valve under low-temperature conditions.

In the drawings, like reference characters designate similar parts in the several views.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a top plan view of a downdraft carburetor showing a preferred form of the invention.

FIG. 2 is a side elevational view thereof, as seen from the bottom of FIG. 1.

FIG. 3 is a vertical sectional view as taken on the line 3-3 of FIG. l.

FIG. 4 is an enlarged vertical sectional view of the metering valve of the invention.

FIG. 5 is a similarly enlarged and broken vertical sectional view as taken on the plane of the line '5-5 of FIG. 1.

FIG. 6 is an enlarged vertical sectional view, on a plane parallel to that of FIG. 2, of the cam assembly of the invention.

FIG. 7 is a broken vertical sectional view showing a modified form of the invention.

FIG. 8 is a broken side elevational view, partly in section of another forni of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the preferred form shown in FIGS. l to 6, the housing 10 is formed with an air inlet passage 30 in its upper portion, with a restricted passage 31 defined by an inwardly and downwardly sloping face 32 above the passage 31, a downwardly and outwardly sloping face 33 below said passage 31, a generally cylindrical passage 34 below the face 33, and a conically flaring passage enlargement 35 below the passage 34. In practice, the passage 31 and faces 32 and 33 are formed on a ring member 36 fitted into an enlargement 37 of the passage 30, and the face 34 is formed on a ring member 38 fitted in said passage enlargement below the ring member 36, both ring members being retained in fixed position by a snap ring 39 engaged with the lower edge of the member 38.

Said housing 10 is provided with a mounting hub 40 axially disposed in the passage 30 and connected to the housing by four spider arms 41. In a similar manner, a boss 42 is coaxially held by spider arms 43 that extend from the ring member 38. An outer enlargement 44 is provided on the upper end of the housing for the filter means 11, inlet 12 and pressure regulator 13, a boss 45 for guiding the means 23, a boss 46 for bearing the arm 21 and lever 22, a flange 47 for engagement with an air filter or a connection duct thereto, and mounting flanges 48 for connection to an intake manifold or a connection thereto.

The filter means 11 is housed in a chamber 49 formed in the enlargement 44 of the housing 10, the same, at the bottom, being open to the inlet 12, and closed at the top by a cap 50. A filter unit, preferably of sintered bronze, 51 is disposed in said chamber and resiliently held by a spring 52 in position over the inlet 12 :and with clearance between itself and the wall of said chamber 49 -so a pool of fuel 53 may be accommodated between the filter and said chamber wall. An outlet passage 54 extends from the lower portion of the chamber through the topof the housing enlargement 44 and terminates in a flexible tube forming the outlet 14. Said chamber 49, between the cap and the filter unit 51, defines `an upper space for vapors :released by the liquid fuel. An .outlet passage 56 extends -laterally from said upper space.

The regulator 13 is formed as check valve having a ball 57 biased by a spring 58 against a seat 59 in an enlargement of the passage 56. Said spring 58 has a predetermined pressure on the ball as, for instance, four pounds, the same being maintained by a plug 60 backing up the spring. The passage 56 conducts the excess of fuel from the chamber 49 toward the return 61 to the tank, such return flow being had when the pressure in said chamber exceeds the relief pressure of the regulator 13. Therefore, only fuel at the predetermined pressure will be conducted through the flexible tube 14. Some of the vapor in the space 55 will exit by way of the passage 56, but most of it will vent through a passage 62 for return through the outlet to the tank.

The metering valve assembly 16, best shown in FIG. 4, is mounted on the hub 40. The same comprises an outer tubular retainer 63 having an upper flange 64 and slidingly fitted in an axial through bore in said hub, a threadedly adjustable split spacer collar 65 supporting said retainer `by its flange, and a compression spring 66 biasing the retainer in an upward direction. A cap member 67 closes the bore 68 of the retainer at the top, and an inwardly directed flange `69 on the lower end of the retainer forms a ledge at said end.

Said assembly 16 further comprises a fuel tube 70 that has an enlargement 71 that rests upon said ledge 69, is slidingly fitted in axial bores in the retainer 63 and its cap member 67, and a compression spring 72 around said tube that acts to exert a positioning bias of the tube enlargement 71 on the mentioned ledge. The upper end of said spring exerts an upward bias on the cap member 67. The tube is connected, by the tube 14, to the outlet passage 54 from the fuel inlet chamber 49.

The fuel-metering disc 17, with but little clearance, is normally located in the restricted portion 31 of the through passage 18 in the housing 10. Said disc is mounted on the reduced portion 73 of a stem 74 that is guided in the boss 42, said stem being coaxial with the tube 70. A conical upper extension 75 on the stem portion 73 is provided with the upwardly extending and tapered metering needle 19 which passes through a port 76 in the end of the tube 70. The lower thicker end of the needle fits said port with minimal clearance--a `matter of about .001 to .002 inch-so the tube 70 and needle 19 may move relatively vertically from said normal position of the disc 17, as retained by the accelerator arm 21. It will be clear that the passage formed between the needle and the port 76 increases in size as the disc 17 is moved in a direction away from the valve assembly 16.

The arm 21 is carried on a pivot shaft 77 which is journaled in the support 78 that is threadedly engaged in the lower portion of the housing 10. A lever 79 on the inner end of said shaft 77 is provided with a roller 80 that is aligned with the end of the stem 74. A forward projection 81 is provided on the outer end of the ysupport 78 and constitutes a stationary bearing for a striker member 82 that is a component of the cam assembly 24. The lever 22 is mounted on and keyed to the outer end of the shaft 77 and, in typical manner, is connected to the accelerator or throttle pedal. Thus, the roller 80, normally in raised position as shown, may be moved by action of said pedal to a lowered position to create a gap, between the stem 74 and itself, that varies according to the degree of pedal depression. Thus, as indicated, said lever 22 constitutes a variable-limit stop for the stem 74 and the needle 19 on the upper end thereof.

The means 23 is shown as a striker pin 83 that is vertically guided in the boss 45 and has a cam-follower end 84 that is downwardly directed. Said pin 83 extends upwardly through a guide nut 85 and has threaded engagement with one end of an arm 86, the other end 86a of which is clamped to the cap member 67. A spring 87 around said pin 83 and between the end 84 thereof and the nut 85, biases said end downwardly. The force of said spring is greater than that of the springs 66 and 72, to normally retain the valve assembly 16 in the position of FIG. 4.

The means 24 is shown as a cam assembly comprising a cam 88 (FIGS. 2, 3 and 6) and the mentioned striker member 82. Said cam 88 is rotationally mounted on a pivot 89 at the side of the housing to which the support 78 is secured, and the striker member is pivotally mounted.

on the mentioned end 81 of said support 78 to be positioned between the arm 22 and the `cam 88.

The cam 88 is formed as a shell having a peripheral wall 90 that is provided with arcuately spaced cam rises 93 and 94. Said cam rises, in this case, are shown as circumferentially spaced The cam is positioned so the end 84 of the pin 83 rides the cam rise 93. The front wall 95 of the cam is provided with a slot 96 through which a fixed stud 97 extends and which limits rotational movement of the cam according to the radial extent of said slot. Said wall 95 is also provided with an outwardly directed stop lug 98.

A bimetallic spring 99 is housed within the hollow of the cam shell with one end thereof anchored, at 100, to the cam wall 95 and the other end to the fixed stud 97, the normal bias of said spring 99 being clockwise, as indicated by the arrow 101.

The striker member 82 is provided with an ear 102 for an adjusting screw 103 engaged with the cam rise 94, with an ear 104 for engaging the lug 98 after the cam has been rotated counterclockwise and moving the cam clockwise, a stop lug 105 to engage a boss 106 on the outside of the housing 10 to limit the acceleration movement of the striker member, and a pair of lugs 107 and 108 directed to have engagement with the opposite edges of the acceleration lever 22.

OPERATION OF THE PREFERRED FORM It is common practice to operate a typical fuel pump at six to ten p.s.i. The present regulator valve 13 has its spring 58 set to allow opening of the valve 13 at four p.s.i., safely below the low pressure level in the fuel line.

The fuel reaching the ilter unit 51 is normally at six to ten p.s.i. and is forced through the porous mass of said lter at such pressure, the filtered fuel then filling chamber 49 to the level of the passage 56. If the pressure in the chamber 49 exceeds four p.s.i., the valve 13 opens, allowing excess fuel to be bypassed back to the fuel tank by way of the outlet 61. As before explained, any vapors entrained in the flow through the passage 56 will return to the fuel tank for re-condensation.

The vapors that are accumulated in the upper part 55 .of chamber 49, due to engine heat or other reason, are carried off by the passage 62. While shown larger, said passage in practice is approximately .030" to .050". The passage 54 to the tube 14 supplies all the fuel necessary for carburetion, the same being free of vapors, either totally or to such degree as to obviate formation of a vapor lock in the fuel supply to the tube 14.

Tube 14 discharges its fuel flow into the fuel tube 70, the bottom of lwhich is normally closed by the engagement between the upper, smaller end of the conical extension 75 vand the lower edge of the port 76. Thus, under forces from beneath, by a backfire, the disc 17, receiving these forces through the conical extension 75, urges the tube 70 upwardly against the bias of the spring 72 while the greater resistance of spring 87 retains the pin 83 in position to counter any forces tending to displace the retainer upwardly. Since a considerable annular space is developed between the edge of the disc .17 and the housing face 32, the backfire gases and pressure are vented.

Twenty-five degree clockwise rotation of the cam member 88 (the limit of slot 96) causes the cam rise 93 to raise the pin 83, thereby actuating the orifice or valve assembly 16 upwardly to bring the port 76 opposite a smaller portion of the needle 19 to provide for an increase of fuel flow through said port. Said cam member 88 also moves clockwise 25 when urged by the throttle lever 22. This lever must be in full open position to so move the cam member, since it is at the time of fullopen throttle that there is need for a richer mixture of fuel, thereby enabling the engine to provide a maximum response to the fuel supplied thereto. Such response is provided whenever the throttle is in wide open position.

At temperatures of 30 F. and lower, the bimetallic spring element 99 holds the cam member 88 in its maximum clockwise position, i.e., with the lower end of the slot 96 engaged with the pin 97, a position assumed by said cam member upon opening of the throttle. This position is maintained until the engine warms up, i.e., there is a temperature of at least 70 F. around the element 99. It is then that said element rotates the cam member 88 to maximum counter-clockwise position, thereby returning the same to normal position, as in FIGS. 2 and 6, thereby restoring the fuel flow through the port 76 to normal.

The ear 104 of the striker 82 engages the lug 98 to cause clockwise rotation of the cam member 88. This is caused by the arm 22 when the throttle is actuated, the lu-g 108 of the striker being engaged by said arm. During this action, -by rotation of the shaft 77, the roller 80 is lowered. This lowering of the stop for the end of the stem 74 allows the disc 17 and the needle 19 to lower, thereby increasing the effective size of the port 76 and the rate of fuel feed for carburetion with air from above.

The lug 107, when engaged by the lever 22 on easing off on the throttle, returns the striker 82 to its retracted position, as in FIG. 2.

The adjusting stop screw 103 engages the cam rise 94, the adjustment allowing for control of idling speed. This cam rise operates in concert with the cam rise 93 to increase idling speed when the engine is operating under cold conditions.

In the modification of FIG. 7, a vacuum piston 110 is substituted for the member 83 of the preferred form and is nonadjustably aixed to the arm 86, the same being disposed in a cylinder 1.11 formed in the housing and is open at its bottom, by a metered passageway 112, to the passage 18 below the disc 17 and, therefore, to engine vacuum in said passage 18. The passageway 112 affords a means for controlling access of vacuum to the bottom of the piston 110. Said vacuum acts against the bias of spring 66 of the valve assembly 16.

At partial throttle with`the engine operating under moderate load, the engine vacuum will have a value sufficiently high to pull downwardly on the piston 110, arm 86, and assembly 63, 64 and 70 against the bias of spring 66, to cause a lean, cruising relationship between orifice 76 and needle 19. This provides an economical setting, as regards fuel consumption. Upon advance of the throttle under load increase, the vacuum will be lowered to a value that exerts a lesser downward force on the pistori 110 and to a value lower than the force of the spring 66. Therefore, said spring will lift the orifice assembly to a fuel-enriching position by opening the orifice 76 for greater fuel ow into the air draft in the passage 18 of body 10.

An adjustable stop 113 is provided to arrest the upward movement of the mentioned assembly to a predetermined amount of travel, thereby placing a value in the extent of fuel enrichment.

In the modification of FIG. 8, a diaphragm assembly 114 is located on the outside of the housing 10, the same replacing the cam assembly 88 of the form of the invention, as in FIGS. 1 to 6. Said diaphragm assembly is shown as having an outer chamber .115 open to atmosphere, an inner chamber 116 open to engine vacuum through a tube 117 that leads to the passage 18 below the disc 17, a flexible membrane 118 separating said chambers. A balancing spring 119 in chamber 116 serves to resist atmospheric pressure on the outside of said diaphragm, thereby holding a slotted link 120 projected. A rock lever 121 has one arm engaged in the slot of link 120, the other arm engaged with the lower end of a pin 122 which is substituted for the member 83.

Engine-controlled vacuum in the chamber 116 lowers the pressure in said chamber allowing atmospheric pres- `sure to overcome the bias of spring 1.19, thereby causing the membrane 118 to be drawn inwardfy. The link 120 on said membrane moves inwardly rocking the lever 121 in a direction to pull downwardly on the pin 122, thus duplicating the function performed by the means of FIG. 7.

The combined forces of spring 66 and the spring 119, of FIG. 8, bear similar relationship tot the greater crosssectional area of the membrane 118 as does said spring 66 alone, in relation to the lesser cross-sectional area of the vacuum piston of FIG. 7, the same being adjustable to function similarly under similar vacuum conditions.

In the form of FIG. 8, adjustability between the pin 122 and the arm 86 is desired, as before.

While the foregoing has illustrated and described what is now contemplated to be the best mode of carrying out the invention, the constructions are, of course, subject to modification without departing from the spirit and scope of the invention. Therefore, it is not desired to restrict the invention to the particular forms of construction illustrated and described, but to cover all modifications that may fall within the scope of the appended claims.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. In a downdraft carburetor having a housing with a vertical passage, with a disc mounted for vertical movement in said passage, and with a tapered needle extending upwardly from said disc,

(a) a valve assembly above and into which said needle extends and having a port controlled by said needle,

(b) means resiliently mounting said .assembly for axial movement relative to the needle,

(c) means, including a flexible connection to the valve assembly and leading to said port, to conduit liquid fuel thereto for carburetion mixture with downdraft air in said passage,

(d) a combination fuel filter and vapor separator in the fuel line to the flexible connection and housed in said housing,

(e) means to bypass the vapors and to return the same to storage,

(f) the filter comprising:

( 1) a chamber between the fuel inlet and the flexible connection with a passage from the bottom of said chamber to said connection,

(2) a sintered metal filter unit in said chamber,

and

(3) means to resiliently hold said unit in the path of fuel flow into said chamber,

(4) a vapor-accumulating space being provided above said unit,

(g) a pre-set pressure regulator housed in said housing to relieve pressure in the flow to the flexible connection above the set pressure of the regulator,

(h) temperature-controlled cam means to shift the port of the resiliently-mounted valve assembly to change the effective size of the port as controlled by the needle, and

(i) a spring having a bias greater than and counter to the resilient mount of the valve assembly to retain 7 8 the same in a position relative to the needle that References Cited closes the port to fuel flow. UNITED STATES PATENTS 2. In a downdraft carburetor according to clalm 1, sa1d 1,972,374 9/1934 Branigan' Cam means Cmpfsmg- 2,646,265 771953 Bareham et a1. 261414 X (a) a rotatlonally mounted cam having one cam rise to 5 2,98 51,1 60 5/1961 Armstrong sh1ft the mentloned port under temperature control, 2,988 345 6/1961 Kolbe et al. and a second cam rise to shift the port under throttle 3,0161345 1/1962 Price- Control, 3,281,130 10/1966 Braun et a1. (b) a striker operatively associated with said cam, and 3,285,585 11/1966 Mennessom (c) a throttle-controlled lever arm engaged with the 10 3,301,536 1/1967 Swatman et a1 261-44 striker to operate the same to return the cam to nor- 3,3 30,542 7 1967 Taylor. mal position after movement thereof to valveand 3,336,014 8/1967 Shorrock 261-44 X port-shifting position. FOREIGN PATENTS 3. In a downdraft carburetor according to claim 2: 15 (a) a member to limit the downward movement of the 1372580 4/1964 France' disc, TIM R. MILES, Primary Examiner (1b) said member being axed to and movable Iwith the U'S C1. XR,

throttle-controlled lever arm. 261-44, 50, 69 

